Probiotic Supplementation in Chronic Kidney Disease: A Double-blind, Randomized, Placebo-controlled Trial

Chronic Kidney Disease-Associated Itch (CKD-aI) in Children-A Narrative Review

Chronic kidney disease (CKD) is a condition of widespread epidemiology and serious consequences affecting all organs of the organism and associated with significant mortality. The knowledge on CKD is rapidly evolving, especially concerning adults. Recently, more data is also appearing regarding CKD in children. Chronic itch (CI) is a common symptom appearing due to various underlying dermatological and systemic conditions. CI may also appear in association with CKD and is termed chronic kidney disease-associated itch (CKD-aI). CKD-aI is relatively well-described in the literature concerning adults, yet it also affects children. Unfortunately, the data on paediatric CKD-aI is particularly scarce. This narrative review aims to describe various aspects of CKD-aI with an emphasis on children, based on the available data in this population and the data extrapolated from adults. Its pathogenesis is described in details, focusing on the growing role of uraemic toxins (UTs), as well as immune dysfunction, altered opioid transmission, infectious agents, xerosis, neuropathy and dialysis-associated aspects. Moreover, epidemiological and clinical aspects are reviewed based on the few data on CKD-aI in children, whereas treatment recommendations are proposed as well, based on the literature on CKD-aI in adults and own experience in managing CI in children.

In Vitro Selection of Probiotics, Prebiotics, and Antioxidants to Develop an Innovative Synbiotic (NatuREN G) and Testing Its Effect in Reducing Uremic Toxins in Fecal Batches from CKD Patients

We aimed to develop an innovative synbiotic formulation for use in reducing dysbiosis, uremic toxins (e.g., p-cresol and indoxyl sulfate), and, consequently, the pathognomonic features of patients with chronic kidney disease (CKD). Twenty-five probiotic strains, belonging to lactobacilli and Bifidobacterium, were tested for their ability to grow in co-culture with different vegetable (pomegranate, tomato, and grapes) sources of antioxidants and prebiotics (inulin, fructo-oligosaccharides, and β-glucans). Probiotics were selected based on the acidification rates and viable cell counts. Inulin and fructo-oligosaccharides reported the best prebiotic activity, while a pomegranate seed extract was initially chosen as antioxidant source. The investigation was also conducted in fecal batches from healthy and CKD subjects, on which metabolomic analyses (profiling volatile organic compounds and total free amino acids) were conducted. Two out of twenty-five probiotics were finally selected. After the stability tests, the selective innovative synbiotic formulation (named NatuREN G) comprised Bifidobacterium animalis BLC1, Lacticaseibacillus casei LC4P1, fructo-oligosaccharides, inulin, quercetin, resveratrol, and proanthocyanidins. Finally, NatuREN G was evaluated on fecal batches collected from CKD in which modified the viable cell densities of some cultivable bacterial patterns, increased the concentration of acetic acid and decane, while reduced the concentration of nonanoic acid, dimethyl trisulfide, and indoxyl sulfate.

Effects of Synbiotics and Probiotics Supplementation on Serum Levels of Endotoxin, Heat Shock Protein 70 Antibodies and Inflammatory Markers in Hemodialysis Patients: a Randomized Double-Blinded Controlled Trial

The aim of this study was to investigate the effects of probiotic and synbiotic supplementation on serum inflammatory markers, endotoxin, and anti-HSP70 in hemodialysis (HD) patients. This study was a randomized, double-blind, placebo-controlled trial. Seventy-five hemodialysis patients who met the inclusion and exclusion criteria were randomly assigned for 12 weeks to one of the three arms: synbiotics [n = 23; 15 g of prebiotics, 5 g of probiotic powder containing Lactobacillus acidophilus T16, Bifidobacterium bifidum BIA-6, Bifidobacterium lactis BIA-6, and Bifidobacterium longum LAF-5 (2.7 × 10⁷ CFU/g each)], probiotics [n = 23; 5 g probiotics as in synbiotic group with 15 g of maltodextrin in the sachet as placebo], and placebo [n = 19; 20 g of maltodextrin in the sachet]. Blood and feces were collected at baseline and after intervention. Serum high sensitive C-reactive protein (hs-CRP), interleukin-6, endotoxin, and anti-heat shock protein 70 antibodies (anti-HSP70) were measured. The number of fecal colonies was determined using the plate-counting method. The mean serum level of hs-CRP, anti-HSP70, and endotoxin decreased significantly between groups (p = 0.007, p = 0.037, and p = 0.036, respectively). For the synbiotic group, the mean changes in hs-CRP and IL-6 were significantly lower than for the placebo (p < 0.001 and p < 0.001, respectively) and probiotic group (p = 0.011 and p = 0.008, respectively). Anti-HSP70 mean changes in the synbiotic and probiotic groups differed from the placebo group (p = 0.002 and p = 0.013, respectively). Administration of synbiotics was more effective than probiotics for improvement of inflammatory markers, endotoxin and anti-HSP70 serum levels. Trial registration number: IRCT2017041233393N1.

Uraemic solutes as therapeutic targets in CKD-associated cardiovascular disease

Chronic kidney disease (CKD) is characterized by the retention of a myriad of solutes termed uraemic (or uremic) toxins, which inflict damage to several organs, including the cardiovascular system. Uraemic toxins can induce hallmarks of cardiovascular disease (CVD), such as atherothrombosis, heart failure, dysrhythmias, vessel calcification and dysregulated angiogenesis. CVD is an important driver of mortality in patients with CKD; however, reliance on conventional approaches to managing CVD risk is insufficient in these patients, underscoring a need to target risk factors that are specific to CKD. Mounting evidence suggests that targeting uraemic toxins and/or pathways induced by uraemic toxins, including tryptophan metabolites and trimethylamine N-oxide (TMAO), can lower the risk of CVD in patients with CKD. Although tangible therapies resulting from our growing knowledge of uraemic toxicity are yet to materialize, a number of pharmacological and non-pharmacological approaches have the potential to abrogate the effects of uraemic toxins, for example, by decreasing the production of uraemic toxins, by modifying metabolic pathways induced by uraemic toxins such as those controlled by aryl hydrocarbon receptor signalling and by augmenting the clearance of uraemic toxins.

Oral iron supplementation in patients with chronic kidney disease: Can it be harmful to the gut microbiota?

Patients with chronic kidney disease (CKD) have several pathophysiological alterations, including anemia, one of the first changes in CKD patients. More recently, researchers have observed that the intestinal microbiota alterations are also another complication in these patients. The most common treatment for anemia is oral (mainly ferrous sulfate) or intravenous iron supplementation. Despite being a necessary treatment, recent studies have reported that supplementation with oral iron may increase its availability in the intestine, leading to disturbance in the gut microbiota and also to oxidative stress in the enterocytes, which may change the permeability and the microbiota profile. Although it is a therapy routinely used in patients with CKD, supplementation with oral iron on the gut microbiota has been rarely studied in these patients. Thus, this review will discuss the relationship between iron and the gut microbiota and the possible effects of oral iron supplementation on gut microbiota in patients with CKD.

Alteration of the Gut Microbiome in Chronic Kidney Disease Patients and Its Association With Serum Free Immunoglobulin Light Chains

Objectives

Gut dysbiosis is associated with chronic kidney disease (CKD), and serum free immunoglobulin light chains (FLCs) are biomarkers for CKD. This study aims to assess the CKD gut microbiome and to determine its impact on serum FLC levels.

Methods

To control for confounders, 100 patients and sex- and age-matched healthy controls (HCs) were recruited. The gut microbiome was assessed by sequencing 16S rRNA gene V3-V4 hypervariable regions. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States was applied to infer functional metabolic pathways. When observing group differences in the microbiome and predicted metabolic pathways, demographic confounders were adjusted using binary logistic regression; when examining impacts of the gut microbiome and metabolic pathways on serum FLCs, factors influencing FLC levels were adjusted using multiple regression.

Results

Principal coordinate analysis revealed a significantly different bacterial community between the CKD and HC groups (P < 0.05). After adjusting for confounders, lower Chao 1, observed species and Shannon indices based on binary logistic regression predicted CKD prevalence. Actinobacteria, Alistipes, Bifidobacterium and Bifidobacterium longum enrichment, upregulation of metabolic pathways of bacterial toxin, chloroalkane and chloroalkene degradation, and Staphylococcus aureus infection also predicted CKD prevalence (P < 0.05). Furthermore, depletion of Actinobacteria and Bifidobacterium and reduced chloroalkane and chloroalkene degradation predicted high levels of FLC λ (P < 0.05).

Conclusions

Gut dysbiosis in CKD patients was confirmed by controlling for confounders in the present study. Additionally, the association between gut dysbiosis and FLC λ levels demonstrates the existence of crosstalk between the microbiome and immune response in CKD.

Protein-bound uremic toxin lowering strategies in chronic kidney disease: a systematic review and meta-analysis

INTRODUCTION

Accumulation of protein-bound uremic toxins, including indoxyl sulfate and p-cresyl sulfate, are associated with increased cardiovascular disease and mortality in chronic kidney disease (CKD). We performed a systematic review and meta-analysis to synthesize the available strategies for lowering protein-bound uremic toxin levels in CKD patients.

METHODS

We conducted a meta-analysis by searching the databases of MEDLINE, Scopus, and the Cochrane Central Register of Controlled Trials for observational studies and randomized controlled trials (RCTs) that examined the effect of dietary protein restrictions, biotic supplements (including prebiotics, probiotics, and synbiotics), AST-120, dialysis techniques, and the outcome of preservation of residual renal function (RRF) on indoxyl sulfate and p-cresyl sulfate levels. Random-effect model meta-analyses were used to compute changes in the outcomes of interest.

RESULTS

A total of 38 articles (2,492 patients), comprising 28 RCTs, 8 single-arm or prospective cohort studies, and 2 cross-sectional studies were included in this meta-analysis. When compared with placebo, prebiotics, synbiotics, and AST-120 provided significantly lower levels of both serum indoxyl sulfate and p-cresyl sulfate. There were no significant reductions in serum indoxyl sulfate and p-cresyl sulfate levels in patients receiving probiotics. Preservation of RRF in dialysis patients resulted in lower levels of both of the protein-bound uremic toxins. When compared with conventional hemodialysis, hemodiafiltration significantly decreased serum p-cresyl sulfate alone, whereas a significant change in serum indoxyl sulfate levels was observed only in studies with long-term observation periods. Very low protein diet (VLPD) and other oral medications yielded insignificant differences in protein-bound uremic toxins.

CONCLUSIONS

The present meta-analysis demonstrated that prebiotics, synbiotics, and AST-120 can effectively reduce both serum indoxyl sulfate and p-cresyl sulfate in CKD patients when compared with placebo. Preservation of RRF was associated with lower serum indoxyl sulfate and p-cresyl sulfate levels. The effect of biotic supplements was detected only in dialysis patients. For non-dialysis CKD patients, the results were limited due to the small number of studies. Further studies are needed to determine the efficacy in these populations.

Can curcumin supplementation reduce plasma levels of gut-derived uremic toxins in hemodialysis patients? A pilot randomized, double-blind, controlled study

BACKGROUND

Gut dysbiosis is common in patients with chronic kidney disease (CKD) and is closely related to inflammatory processes. Some nutritional strategies, such as bioactive compounds present in curcumin, have been proposed as an option to modulate the gut microbiota and decrease the production of uremic toxins such as indoxyl sulfate (IS), p-cresyl sulfate (pCS) and indole-3 acetic acid (IAA).

OBJECTIVE

To evaluate the effects of curcumin supplementation on uremic toxins plasma levels produced by gut microbiota in patients with CKD on hemodialysis (HD).

METHODS

Randomized, double-blind trial in 28 patients [53.6 ± 13.4 years, fourteen men, BMI 26.7 ± 3.7 kg/m², dialysis vintage 37.5 (12-193) months]. Fourteen patients were randomly allocated to the curcumin group and received 100 mL of orange juice with 12 g carrot and 2.5 g of turmeric and 14 patients to the control group who received the same juice but without turmeric three times per week after HD sessions for three months. IS, pCS, IAA plasma levels were measured by reverse-phase high-performance liquid chromatography RESULTS: After three months of supplementation, the curcumin group showed a significant decrease in pCS plasma levels [from 32.4 (22.1-45.9) to 25.2 (17.9-37.9) mg/L, p = 0.009], which did not occur in the control group. No statistical difference was observed in IS and IAA levels in both groups.

CONCLUSION

The oral supplementation of curcumin for three months seems to reduce p-CS plasma levels in HD patients, suggesting a gut microbiota modulation.

Intestinal alkaline phosphatase modulation by food components: predictive, preventive, and personalized strategies for novel treatment options in chronic kidney disease

Alkaline phosphatase (AP) is a ubiquitous membrane-bound glycoprotein that catalyzes phosphate monoesters' hydrolysis from organic compounds, an essential process in cell signaling. Four AP isozymes have been described in humans, placental AP, germ cell AP, tissue nonspecific AP, and intestinal AP (IAP). IAP plays a crucial role in gut microbial homeostasis, nutrient uptake, and local and systemic inflammation, and its dysfunction is associated with persistent inflammatory disorders. AP is a strong predictor of mortality in the general population and patients with cardiovascular and chronic kidney disease (CKD). However, little is known about IAP modulation and its possible consequences in CKD, a disease characterized by gut microbiota imbalance and persistent low-grade inflammation. Mitigating inflammation and dysbiosis can prevent cardiovascular complications in patients with CKD, and monitoring factors such as IAP can be useful for predicting those complications. Here, we review IAP's role and the results of nutritional interventions targeting IAP in experimental models to prevent alterations in the gut microbiota, which could be a possible target of predictive, preventive, personalized medicine (PPPM) to avoid CKD complications. Microbiota and some nutrients may activate IAP, which seems to have a beneficial impact on health; however, data on CKD remains scarce.

Food as medicine: targeting the uraemic phenotype in chronic kidney disease

The observation that unhealthy diets (those that are low in whole grains, fruits and vegetables, and high in sugar, salt, saturated fat and ultra-processed foods) are a major risk factor for poor health outcomes has boosted interest in the concept of 'food as medicine'. This concept is especially relevant to metabolic diseases, such as chronic kidney disease (CKD), in which dietary approaches are already used to ameliorate metabolic and nutritional complications. Increased awareness that toxic uraemic metabolites originate not only from intermediary metabolism but also from gut microbial metabolism, which is directly influenced by diet, has fuelled interest in the potential of 'food as medicine' approaches in CKD beyond the current strategies of protein, sodium and phosphate restriction. Bioactive nutrients can alter the composition and metabolism of the microbiota, act as modulators of transcription factors involved in inflammation and oxidative stress, mitigate mitochondrial dysfunction, act as senolytics and impact the epigenome by altering one-carbon metabolism. As gut dysbiosis, inflammation, oxidative stress, mitochondrial dysfunction, premature ageing and epigenetic changes are common features of CKD, these findings suggest that tailored, healthy diets that include bioactive nutrients as part of the foodome could potentially be used to prevent and treat CKD and its complications.

Beverages Rich in Resveratrol and Physical Activity Attenuate Metabolic Changes Induced by High-Fat Diet

Consumption of saturated fat causes deleterious effects on health, which could be minimized through physical activity and foods with functional characteristics consumption. The aim of the study was to evaluate the beverage rich in resveratrol consumption and physical exercise in gut microbiota, body composition, lipid peroxidation, interleukin-6 (IL6) concentration and systolic blood pressure (SBP) of rats to the high-fat diet. Wistar rats were fed with control diet, high-fat diet (HFD), HFD and 15 mL solution of resveratrol, HFD and 15 mL of grape juice, HFD and 10 mL of red wine. All animals performed the physical training protocol five days a week. Grape juice and red wine composition were analyzed, SBP, body mass, consumption, adiposity and body composition, gut microbiota, lipid peroxidation and inflammation were evaluated. The grape juice (114.8 ± 22.5 mmHG) and red wine (129 ± 15.8 mmHg) groups showed lower SBP when compared to HFD (216.8 ± 20.6 mmHg) (p < 0.0001). The grape juice group (GJG) (39.1 ± 7) had a higher number of microbiota bands DNA when compared to the other groups (p = 0.002). The GJG (33.7 ± 6.7 pg/mL) presented lower concentration IL6 when compared to high-fat group (47.3 ± 16 pg/mL) (p = 0.003). GJG (4.7 ± 1.2 nmol/L) presented a lower concentration of TBARS when compared to control group (6.1 ± 1.4 nmol/L) and resveratrol group (6.6 ± 0.9 nmol/L), and the red wine group (7.4 ± 1.2 nmol/L) had a higher concentration of TBARS when compared to control group and GJG (p = 0.0001). The consumption of these beverages, especially grape juice, together with physical exercise, was able to promote beneficial changes even in the presence of a HFD.

Gut-Derived Protein-Bound Uremic Toxins

Chronic kidney disease (CKD) afflicts more than 500 million people worldwide and is one of the fastest growing global causes of mortality. When glomerular filtration rate begins to fall, uremic toxins accumulate in the serum and significantly increase the risk of death from cardiovascular disease and other causes. Several of the most harmful uremic toxins are produced by the gut microbiota. Furthermore, many such toxins are protein-bound and are therefore recalcitrant to removal by dialysis. We review the derivation and pathological mechanisms of gut-derived, protein-bound uremic toxins (PBUTs). We further outline the emerging relationship between kidney disease and gut dysbiosis, including the bacterial taxa altered, the regulation of microbial uremic toxin-producing genes, and their downstream physiological and neurological consequences. Finally, we discuss gut-targeted therapeutic strategies employed to reduce PBUTs. We conclude that targeting the gut microbiota is a promising approach for the treatment of CKD by blocking the serum accumulation of PBUTs that cannot be eliminated by dialysis.

The Efficacy of Lactobacillus-Containing Probiotic Supplementation in Hemodialysis Patients: A Randomized, Double-Blind, Placebo-Controlled Trial

OBJECTIVES

This study was performed to determine the effects of probiotic supplementation on cholesterol-triglyceride ratio, an indirect marker of insulin resistance, protein-bound uremic toxins, biomarkers of inflammation, and microbial translocation in end-stage renal disease patients on hemodialysis.

METHODS

Fifty-six patients aged 39-75 years were assigned into two groups to receive either probiotic sachets (n = 28) or a placebo (n = 28) in a randomized double-blinded placebo-controlled clinical trial. The patients in the probiotic group received twice daily sachets that contained a mixture of three viable and freeze-dried strains: Lactococcus lactis subsp. Lactis LL358, Lactobaccillus salivarius LS159, and Lactobaccillus pentosus LPE588 at high dose (100 billion; 1 × 10¹¹ cfu/day) for 6 months.

RESULTS

A total of 50 patients were available for final analysis. Probiotic supplementation did not have a significant influence on cholesterol-triglyceride ratio. Probiotic supplementation for 6 months caused a significant decrease in serum levels of indoxyl sulfate. Compared with the placebo, probiotic supplementation did not result in significant changes in hemoglobin levels, blood urea nitrogen, blood glucose, serum p-cresyl sulfate, inflammatory, and microbial translocation markers. No clinically significant changes in body composition were observed between the two groups during the study period. The probiotic supplementation was well tolerated by all subjects with minimal adverse effects during the 6-month-long study.

CONCLUSION

Our results suggest that high-dose multistrain lactobaccillus probiotic supplementation over 6 months as a monotherapy did not significantly decrease markers of insulin resistance, cholesterol-triglyceride ratio, and most of the studied markers, with the exception of levels of indoxyl sulfate in patients on HD.

Pilot Study of Probiotic Supplementation on Uremic Toxicity and Inflammatory Cytokines in Chronic Kidney Patients

Background:

Bacterial metabolism contributes to the generation of uremic toxins in patients with chronic kidney disease (CKD). It has been investigated the use of probiotics in the reduction of uremic toxins intestinal production.

Objective:

The aim of this pilot study was to evaluate the effect of probiotic supplementation on reducing the production of uremic toxins and the inflammatory profile of CKD patients.

Methods:

We performed a randomized, blind, placebo-controlled, crossover study on patients with CKD stages 3 and 4. The intervention was a probiotic formulation composed of Lactobacillus acidophilus strains given orally three times a day for 3 months. Changes in uremic toxins (p-Cresylsulfate and Indoxyl Sulfate) and serum inflammatory cytokines were the primary endpoints.

Results:

Of the 44 patients randomized, 25 completed the study (mean age 51 ± 9.34, 64% female, mean eGFR 36 ± 14.26 mL/min/1.73m², mean BMI 28.5 ± 5.75 kg/m²). At 3 months, there were no significant changes in any of the studied biomarkers including p-cresylsulfate (p = 0.57), Indoxyl sulfate (p = 0.08) and interleukin-6 (p = 0.55).

Conclusion:

Lactobacillus acidophilus strains given as probiotic were not able to reduce serum levels of uremic toxins and biomarkers of inflammation in CKD patients in stage 3 and 4.

The food-gut axis: lactic acid bacteria and their link to food, the gut microbiome and human health

Lactic acid bacteria (LAB) are present in foods, the environment and the animal gut, although fermented foods (FFs) are recognized as the primary niche of LAB activity. Several LAB strains have been studied for their health-promoting properties and are employed as probiotics. FFs are recognized for their potential beneficial effects, which we review in this article. They are also an important source of LAB, which are ingested daily upon FF consumption. In this review, we describe the diversity of LAB and their occurrence in food as well as the gut microbiome. We discuss the opportunities to study LAB diversity and functional properties by considering the availability of both genomic and metagenomic data in public repositories, as well as the different latest computational tools for data analysis. In addition, we discuss the role of LAB as potential probiotics by reporting the prevalence of key genomic features in public genomes and by surveying the outcomes of LAB use in clinical trials involving human subjects. Finally, we highlight the need for further studies aimed at improving our knowledge of the link between LAB-fermented foods and the human gut from the perspective of health promotion.

The gut microbiota profile of adults with kidney disease and kidney stones: a systematic review of the literature

Background

There is mounting evidence that individuals with kidney disease and kidney stones have an abnormal gut microbiota composition. No studies to date have summarised the evidence to categorise how the gut microbiota profile of these individuals may differ from controls. Synthesis of this evidence is essential to inform future clinical trials. This systematic review aims to characterise differences of the gut microbial community in adults with kidney disease and kidney stones, as well as to describe the functional capacity of the gut microbiota and reporting of diet as a confounder in these studies.

Methods

Included studies were those that investigated the gut microbial community in adults with kidney disease or kidney stones and compared this to the profile of controls. Six scientific databases (CINHAL, Medline, PubMed, Scopus, Web of Science and Cochrane Library), as well as selected grey literature sources, were searched. Quality assessment was undertaken independently by three authors. The system of evidence level criteria was employed to quantitatively evaluate the alteration of microbiota by strictly considering the number, methodological quality and consistency of the findings. Additional findings relating to altered functions of the gut microbiota, dietary intakes and dietary methodologies used were qualitatively summarised.

Results

Twenty-five articles met the eligibility criteria and included data from a total of 892 adults with kidney disease or kidney stones and 1400 controls. Compared to controls, adults with kidney disease had increased abundances of several microbes including Enterobacteriaceae, Streptococcaceae, Streptococcus and decreased abundances of Prevotellaceae, Prevotella, Prevotella 9 and Roseburia among other taxa. Adults with kidney stones also had an altered microbial composition with variations to Bacteroides, Lachnospiraceae NK4A136 group, Ruminiclostridium 5 group, Dorea, Enterobacter, Christensenellaceae and its genus Christensenellaceae R7 group. Differences in the functional potential of the microbial community between controls and adults with kidney disease or kidney stones were also identified. Only three of the 25 articles presented dietary data, and of these studies, only two used a valid dietary assessment method.

Conclusions

The gut microbiota profile of adults with kidney disease and kidney stones differs from controls. Future study designs should include adequate reporting of important confounders such as dietary intake to assist with interpretation of findings.

Inulin-type fructan intervention restricts the increase in gut microbiome-generated indole in patients with peritoneal dialysis: a randomized crossover study

BACKGROUND

Indoxyl sulfate (IS) and p-cresyl sulfate (pCS), 2 important protein-bound uremic toxins, are independent risk factors for cardiovascular disease in patients with end-stage renal disease. Indole and p-cresol are gut microbiome-generated precursors of IS and pCS.

OBJECTIVE

The aim of the present study was to determine whether inulin-type fructans (ITFs) reduce the production of indole and p-cresol by altering their producing bacteria in patients with peritoneal dialysis.

METHODS

Patients receiving peritoneal dialysis for >3 mo without diabetes and not using antibiotics were recruited to a randomized, double-blind, placebo-controlled, crossover trial of ITF intervention over 36 wk (12-wk washout). The primary outcomes were gut microbiome, fecal indole and p-cresol, indole-producing bacteria, p-cresol-producing bacteria, and serum IS and pCS. The secondary outcomes were fecal pH, 24-h urine, and dialysis removal of IS and pCS.

RESULTS

Of 21 individuals randomly assigned, 15 completed the study. The daily nutrient intakes, including protein, tryptophan, and tyrosine, were isostatic during the prebiotic, washout, and placebo intervention. There were no baseline differences in the outcomes of interest between treatments. For fecal indole, its concentrations did not change significantly in either treatment. However, there was a trend toward the treatment-by-time effect (P = 0.052), with a quantitative reduction in the ITF treatment and an increase in the control. The difference in the changes between the 2 treatments was significant (-10.07 ± 7.48 μg/g vs +13.35 ± 7.66 μg/g; P = 0.040). Similar to Bacteroides thetaiotaomicron, there was a difference over time between the 2 treatments, with a significant treatment and time interaction effect (P = 0.047). There were no treatment, time, or interaction effects for fecal p-cresol, serum IS and pCS, 24-h urine, and dialysis removal of IS and pCS.

CONCLUSIONS

Our results suggested that ITFs restricted the increase in gut microbiome-generated indole in patients with peritoneal dialysis. This trial was registered at http://www.chictr.org.cn/showproj.aspx?proj=21228 as ChiCTR-INR-17013739.

Clinical utility of characterizing intestinal flora in septic kidney injury

The incidence of septic acute kidney injury (AKI) is increasing, it has become a major threat to human health because of its acute onset, poor prognosis, and high hospital costs. The most common cause of AKI in critical-care units is sepsis. Septic AKI is a complex and multi-factorial process; its pathogenesis is not fully understood. In sepsis, the destruction of mucosal barriers, intestinal flora disorders, intestinal ischemia/reperfusion injury, use of antibiotics, and lack of intestinal nutrients lead to an inflammatory reactions that in turn affects the metabolism and immunity of the host. Such changes further influence the occurrence and development of AKI. New technology is enabling various detection methods for intestinal flora. Clinical application of these methods in septic renal injury is expected to clarify the relationship among pathogenesis, disease progression mechanism, and intestinal flora.

Efficacy of Divinylbenzenic Resin in Removing Indoxyl Sulfate and P-Cresol Sulfate in Hemodialysis Patients: Results From an In Vitro Study and An In Vivo Pilot Trial (xuanro4-Nature 3.2)

High serum levels of microbiota-derived uremic toxins, indoxyl sulfate (IS) and p-cresyl sulfate (PCS), are associated with chronic kidney disease (CKD) progression and cardiovascular complications. IS and PCS cannot be efficiently removed by conventional hemodialysis (HD), due to their high binding affinity for albumin. This study evaluates the efficacy of a divinylbenzene-polyvinylpyrrolidone (DVB-PVP) cartridge and a synbiotic to reduce uremic toxins in HD patients. First, the in vitro efficacy of DVB-PVP in adsorbing IS and PCS was evaluated. Second, a randomized, placebo-controlled pilot study in HD patients was carried out to establish whether the administration of a synbiotic, either individually and in association with DVB-PVP-HD, could reduce the production of uremic toxins. In vitro data showed that DVB-PVP resin removed a mean of 56% PCS and around 54% IS, after 6 h of perfusion. While, in the in vivo study, the DVB-PVP cartridge showed its adsorbing efficacy only for IS plasma levels. The combination of synbiotic treatment with DVB-PVP HD decreased IS and PCS both at pre- and post-dialysis levels. In conclusion, this study provides the first line of evidence on the synergistic action of gut microbiota modulation and an innovative absorption-based approach in HD patients, aimed at reducing plasma levels of IS and PCS.

Effects of Probiotic Supplementation on Trimethylamine-N-Oxide Plasma Levels in Hemodialysis Patients: a Pilot Study

Components present in the diet, L-carnitine, choline, and betaine are metabolized by gut microbiota to produce metabolites such as trimethylamine-N-oxide (TMAO) that appear to promote cardiovascular disease in chronic kidney disease (CKD) patients. The objective of this pilot study was to evaluate the effects of probiotic supplementation for 3 months on plasma TMAO levels in CKD patients on hemodialysis (HD). A randomized, double-blind trial was performed in 21 patients [54.8 ± 10.4 years, nine men, BMI 26.1 ± 4.8 kg/m², dialysis vintage 68.5 (34.2-120.7) months]. Ten patients were randomly allocated to the placebo group and 11 to the probiotic group [three capsules, totaling 9 × 10¹³ colony-forming units per day of Streptococcus thermophilus (KB19), Lactobacillus acidophilus (KB27), and Bifidobacteria longum (KB31). Plasma TMAO, choline, and betaine levels were measured by LC-MS/MS at baseline and after 3 months. While TMAO did not change after probiotic supplementation, there was a significant increase in betaine plasma levels. In contrast, the placebo group showed a significant decrease in plasma choline levels. Short-term probiotic supplementation does not appear to influence plasma TMAO levels in HD patients. Long-term studies are needed to determine whether probiotics may affect TMAO production in CKD patients.

The effect of probiotics on inflammatory biomarkers: a meta-analysis of randomized clinical trials

PURPOSE

No study has summarized earlier findings on the effect of probiotic supplementation on inflammatory biomarkers. This systematic review and meta-analysis was conducted to systematically review the available placebo-controlled clinical trials about the effect of probiotic supplementation on several inflammatory biomarkers in adults.

METHODS

Relevant papers published up to March 2018 were searched up through PubMed, MEDLINE, SCOPUS, EMBASE, and Google Scholar, using following suitable keywords. Clinical trials that examined the effect of probiotic supplementation on inflammation in adults were included.

RESULTS

Overall, 42 randomized clinical trials (1138 participants in intervention and 1120 participants in control groups) were included. Combining findings from included studies, we found a significant reduction in serum hs-CRP [standardized mean difference (SMD) - 0.46; 95% CI - 0.73, - 0.19], TNF-a (- 0.21; - 0.34, - 0.08), IL-6 (- 0.37; - 0.51, - 0.24), IL-12 (- 0.47; - 0.67, - 0.27), and IL-4 concentrations (- 0.48; - 0.76, - 0.20) after probiotic supplementation. Pooling effect sizes from 11 studies with 12 effect sizes, a significant increase in IL-10 concentrations was seen (0.21; 0.04, 0.38). We failed to find a significant effect of probiotic supplementation on serum IL-1B (- 0.17; - 0.37, 0.02), IL-8 (- 0.01; - 0.30, 0.28), and IFN-g (- 0.08; - 0.31, 0.15) and IL-17 concentrations (0.06; - 0.34, 0.46).

CONCLUSIONS

Probiotic supplementation significantly reduced serum concentrations of pro-inflammatory cytokines including, hs-CRP, TNF-a, IL-6, IL-12, and IL-4, but it did not influence IL-1B, IL-8, IFN-g, and IL-17 concentrations. A significant increase in serum concentrations of IL-10, as a anti-inflammatory cytokine was also documented after probiotic supplementation.

Resistant starch supplementation attenuates inflammation in hemodialysis patients: a pilot study

PURPOSE

In chronic kidney disease (CKD) patients, dysbiosis is associated with inflammation and cardiovascular risk, so many nutritional strategies are being studied to reduce these complications. Resistant starch (RS) can be considered a prebiotic that promotes many benefits, including modulation of gut microbiota which is linked to immune-modulatory effects. The aim of this study was to evaluate the effects of RS supplementation on proinflammatory cytokines in CKD patients on hemodialysis (HD).

METHODS

A double-blind, placebo-controlled, randomized trial was conducted with sixteen HD patients (55.3 ± 10.05 years, body mass index (BMI) 25.9 ± 5.42 kg/m², 56% men, time on dialysis 38.9 ± 29.23 months). They were allocated to the RS group (16 g RS/day) or placebo group (manioc flour). The serum concentration of ten cytokines and growth factors was detected through a multiparametric immunoassay based on XMap-labeled magnetic microbeads (Luminex Corp, USA) before and after 4 weeks with RS supplementation.

RESULTS

After RS supplementation, there was a reduction of Regulated upon Activation, Normal T-Cell Expressed and Secreted (p < 0.001), platelet-derived growth factor (two B subunits) (p = 0.014) and interferon-inducible protein 10 (IP-10) (p = 0.027). The other parameters did not change significantly.

CONCLUSION

This preliminary result indicates that RS may contribute to a desirable profile of inflammatory markers in CKD patients.

Simultaneous use of oxalate-degrading bacteria and herbal extract to reduce the urinary oxalate in a rat model: A new strategy

Objective:

Urinary stones with oxalate composition can cause kidney failure. Recent findings evidenced that probiotics are effective in reducing oxalate absorption in these subjects based on their high colonic absorption levels at baseline. The purpose of this study was to evaluate the effect of the simultaneous use of oxalate-degrading bacteria, Urtica dioica and T. terrestris extract in reducing urinary oxalate.

Materials and Methods:

Anti-urolithiatic activity of Urtica dioica and T. terrestris extract and probiotic by using ethylene glycol induced rat model. In this study, 4 strains of Lactobacillus and 2 strains of Bifidobacterium and also 2 strains of L. paracasei (that showed high power in oxalate degrading in culture media) were used. Male Wistar rats were divided into four groups (n=6). The rats of group-I received normal diet (positive control group) and groups-II (negative control group), III, IV rats received diet containing ethylene glycol (3%) for 30 days. Groups III rats received Urtica dioica and T. terrestris extract. Groups IV rats received extracts + probiotic for 30 days.

Findings:

The results show that the use of herbal extracts (Urtica dioica and T. terrestris) reduced the level of urinary oxalate and other parameters of urine and serum. Also, the accumulation of calcium oxalate crystals in the kidney tissue was significantly reduced.

Conclusion:

Considering that the formation of calcium oxalate crystals can cause inflammation and tissue damage in the kidney, the use of herbal extracts with oxalate degrading bacteria can be a new therapeutic approach to preventing the formation of kidney stones.

Indoxyl sulfate associates with cardiovascular phenotype in children with chronic kidney disease

BACKGROUND

Cardiovascular disease is the leading cause of death in children with chronic kidney disease (CKD). Serum levels of gut-derived uremic toxins increase with deterioration of kidney function and are associated with cardiac comorbidities in adult CKD patients.

METHODS

Indoxyl sulfate (IS) and p-cresyl sulfate (pCS) were measured by high-performance liquid chromatography in serum of children participating in the Cardiovascular Comorbidity in Children with CKD (4C) Study. Results were correlated with measurements of the carotid intima-media thickness (cIMT), central pulse wave velocity (PWV), and left ventricular mass index (LVMI) in children aged 6-17 years with initial eGFR of 10-60 ml/min per 1.73 m².

RESULTS

The median serum levels of total IS and of pCS, measured in 609 patients, were 5.3 μmol/l (8.7) and 17.0 μmol/l (21.6), respectively. In a multivariable regression model, IS and pCS showed significant positive associations with urea and negative associations with eGFR and uric acid. Furthermore, positive associations of pCS with age, serum albumin, and non-Mediterranean residency and a negative association with glomerular disease were observed. By multivariable regression analysis, only IS was significantly associated with a higher cIMT SDS at baseline and progression of PWV SDS within 12 months, independent of other risk factors.

CONCLUSIONS

Serum levels of gut-derived uremic toxins IS and pCS correlated inversely with eGFR in children. Only IS was significantly associated with surrogate markers of cardiovascular disease in this large pediatric CKD cohort.

The Efficacy of Prebiotic, Probiotic, and Synbiotic Supplementation in Modulating Gut-Derived Circulatory Particles Associated With Cardiovascular Disease in Individuals Receiving Dialysis: A Systematic Review and Meta-analysis of Randomized Controlled Trials

OBJECTIVE

This systematic review and meta-analyses provide an up-to-date synthesis on the effects of supplementation on circulating levels of toxic metabolites, markers of uremia and inflammation, blood lipids, and other clinical outcomes.

METHODS

Seventeen databases were searched, supplemented with internet and hand searching. Randomized controlled trials of adult end-stage renal-disease individuals receiving either hemodialysis or peritoneal dialysis were eligible. Trials were restricted to those which had administered a prebiotic, probiotic, or synbiotic as an oral supplement. Primary outcomes were measures of circulating endotoxin, indoxyl-sulphate, and p-cresyl sulfate.

RESULTS

Twenty-one trials were eligible (1152 randomized participants), of which 16 trials were considered to have a high risk of bias. The number of trials available for meta-analysis varied for each primary outcome. Synthesized data indicated that supplementation significantly reduced circulating levels of endotoxin (standardized mean difference, -0.61; 95% confidence interval, -1.03 to -0.20; P = .004; I² = 0%), indoxyl-sulphate (-0.34; -0.64 to -0.04; P = .02; I² = 0%), and p-cresyl sulfate (-0.34; -0.61 to -0.07; P = .01; I² = 0%). For secondary outcomes, supplementation significantly reduced gastrointestinal symptoms (-0.54; -1.02 to -0.07; P = .02; I² = 0%).

CONCLUSIONS

Supplementation reduces toxic metabolites associated with cardiovascular disease and mortality in individuals receiving dialysis. However, the majority of trials included were low in quality.

The gut microbiota and its relationship with chronic kidney disease

Chronic kidney disease (CKD) is a worldwide health problem, because it is one of the most common complications of metabolic diseases including obesity and type 2 diabetes. Patients with CKD also develop other comorbidities, such as hypertension, hyperlipidemias, liver and cardiovascular diseases, gastrointestinal problems, and cognitive deterioration, which worsens their health. Therapy includes reducing comorbidities or using replacement therapy, such as peritoneal dialysis, hemodialysis, and organ transplant. Health care systems are searching for alternative treatments for CKD patients to mitigate or retard their progression. One new topic is the study of uremic toxins (UT), which are excessively produced during CKD as products of food metabolism or as a result of the loss of renal function that have a negative impact on the kidneys and other organs. High urea concentrations significantly modify the microbiota in the gut also, cause a decrease in bacterial strains that produce anti-inflammatory and fuel molecules and an increase in bacterial strains that can metabolize urea, but also produce UT, including indoxyl sulfate and p-cresol sulfate. UT activates several cellular processes that induce oxidative environments, inflammation, proliferation, fibrosis development, and apoptosis; these processes mainly occur in the gut, heart, and kidney. The study of the microbiota during CKD allowed for the implementation of therapy schemes to try to reduce the circulating concentrations of UT and reduce the damage. The objective of this review is to show an overview to know the main UT produced in end-stage renal disease patients, and how prebiotics and probiotics intervention acts as a helpful tool in CKD treatment.

Gut Dysbiosis and the Intestinal Microbiome: Streptococcus thermophilus a Key Probiotic for Reducing Uremia

In the intestines, probiotics can produce antagonistic effects such as antibiotic–like compounds, bactericidal proteins such as bacteriocins, and encourage the production of metabolic end products that may assist in preventing infections from various pathobionts (capable of pathogenic activity) microbes. Metabolites produced by intestinal bacteria and the adoptions of molecular methods to cross-examine and describe the human microbiome have refreshed interest in the discipline of nephology. As such, the adjunctive administration of probiotics for the treatment of chronic kidney disease (CKD) posits that certain probiotic bacteria can reduce the intestinal burden of uremic toxins. Uremic toxins eventuate from the over manifestation of glucotoxicity and lipotoxicity, increased activity of the hexosamine and polyol biochemical and synthetic pathways. The accumulation of advanced glycation end products that have been regularly associated with a dysbiotic colonic microbiome drives the overproduction of uremic toxins in the colon and the consequent local pro-inflammatory processes. Intestinal dysbiosis associated with significant shifts in abundance and diversity of intestinal bacteria with a resultant and maintained uremia promoting an uncontrolled mucosal pro-inflammatory state. In this narrative review we further address the efficacy of probiotics and highlighted in part the probiotic bacterium Streptococcus thermophilus as an important modulator of uremic toxins in the gut of patients diagnosed with chronic kidney disease. In conjunction with prudent nutritional practices it may be possible to prevent the progression of CKD and significantly downregulate mucosal pro-inflammatory activity with the administration of probiotics that contain S. thermophilus.

Impact of Gut Microbiota Composition on Onset and Progression of Chronic Non-Communicable Diseases

In recent years, mounting scientific evidence has emerged regarding the evaluation of the putative correlation between the gut microbiota composition and the presence of chronic non-communicable diseases (NCDs), such as diabetes mellitus, chronic kidney disease, and arterial hypertension. The aim of this narrative review is to examine the current literature with respect to the relationship between intestinal dysbiosis and the insurgence/progression of chronic NCDs, analyzing the physiopathological mechanisms that can induce microbiota modification in the course of these pathologies, and the possible effect induced by microbiota alteration upon disease onset. Therapy based on probiotics, prebiotics, synbiotics, postbiotics, and fecal microbiota transplant can represent a useful therapeutic tool, as has been highlighted on animal studies. To this moment, clinical studies that intended to demonstrate the beneficial effect induced by this kind of oral supplementation on the gut microbiota composition, and subsequent amelioration of signs and symptoms of chronic NCDs have been conducted on limited sample populations for a limited follow-up period. Therefore, to fully evaluate the therapeutic value of this kind of intervention, it would be ideal to design ample population; randomized clinical trials with a lengthy follow up period.

Effects of probiotic supplements on the progression of chronic kidney disease: A meta-analysis

BACKGROUND

Chronic kidney disease (CKD) is a worldwide public health problem. Although accumulated data suggested that probiotic supplements played roles in CKD, the results remained controversial. Here, we performed a meta-analysis to assess the effects of probiotic supplements on the CKD progression.

METHODS

A systematic search was conducted through the PubMed, Embase and Cochrane databases until September 2018. Randomized controlled trials with control receiving placebo, evaluating the effects of probiotic supplements on CKD were included.

RESULTS

A total of 10 randomized controlled trials in 8 countries were selected. In the meta-analysis, urea level was significantly reduced in probiotics-administrated non-dialysis patients (mean differences (MD) = -30.01; 95% confidence interval (CI) = [-56.78, -3.25]; P = 0.03) while no significant change was found in the dialysis patients receiving probiotics (MD = 0.1; 95% CI = [-9.28, 9.48]; P = 0.98). Probiotic supplements also exhibited no effect on uric acid (MD = -0.43; 95% CI = [-1.19, 0.33]; P = 0.27), C-reactive protein (MD = -0.48; 95% CI = [-1.29, 0.33]; P = 0.24), creatinine (MD = -0.18; 95% CI = [-0.82, 0.47]; P = 0.59), and estimated glomerular filtration rate (MD = 2.10; 95% CI = [-1.31, 5.52]; P = 0.23) of CKD patients.

CONCLUSION

Our results highlighted that probiotic supplements exerted a statistically significant effect on urea levels in non-dialysis CKD population, while no evidence suggested that probiotics possessed meaningful impacts on the reduction of uric acid, C-reactive protein, creatinine and estimated glomerular filtration rate preservation of CKD population.

Effect of probiotic and synbiotic supplementation on inflammatory markers in health and disease status: A systematic review and meta-analysis of clinical trials

The current systematic review and meta-analysis investigated the effect of probiotic/synbiotic on a wide range of inflammatory and anti-inflammatory markers in healthy and various disease conditions. PubMed, SCOPUS and Web of Science databases were searched. All clinical trials which investigated the effect of oral administration of probiotic or synbiotic on inflammatory markers (C-reactive protein (CRP), interleukin (IL) 1β, IL-4, IL-6, IL-8, IL-10, IL-12, tumor necrosis factor (TNF) α, interferon (IFN) γ and transforming growth factor (TGF) β) for more than one week with concurrent control groups were included. One-hundred sixty seven publications was analysed. Results were as follows: CRP decreased in healthy, metabolic disorders, inflammatory bowel disease (IBD), arthritis and critically ill condition but not in renal failure. IL-1B: no change in healthy subjects and arthritis. TNF-α: decreased in healthy, fatty liver, IBD and hepatic cirrhosis, no change in diabetes, metabolic syndrome (MS) + PCOS (polycystic ovary syndrome) and arthritis. IL-6: no change in healthy, metabolic disorders and arthritis, increased in cirrhosis and renal failure, decreased in PCOS + MS. IL-10: no change in healthy, IBD and metabolic disorders, increased in arthritis. IL-4, IL-8, IL-12, IFN-g and TGF-b: no change in healthy subjects. In conclusion, probiotic/synbiotic decreased some of the inflammatory markers. The intervention was most effective in CRP and TNF-α reduction in healthy or disease state. Moreover, the intervention decreased inflammation most effectively in the following disease conditions, respectively: IBD, arthritis, fatty liver. PROSPERO REGISTRATION NUMBER: CRD42018088688.

Major Traditional Probiotics: Comparative Genomic Analyses and Roles in Gut Microbiome of Eight Cohorts

Modulating gut microbiota to promote host health is well recognized. Therefore, people consume dietary products containing traditional probiotics in wishing to improve their health, and they need more research-based advices on how to select products with suitable probiotic species. Probiotic designers are sometimes confused about how to design precision products for different consumers by taking advantages of different probiotic species’ strengths. Additionally, large-scale analyses on traditional probiotic complementarity potentials and their roles in gut microbiome related to common diseases are not well understood. Here, we comprehensively analyzed 444 genomes of major traditional probiotic (sub) species (MTPS, n = 15) by combining one newly sequenced genome with all of the public NCBI-available MTPS-related genomes. The public human fecal metagenomic data (n = 1,815) of eight cohorts were used to evaluate the roles of MTPS, compared to other main gut bacteria, in disease association by examining the species enrichment direction in disease group or the control group. Our work provided a comprehensive genetic landscape and complementarity relations for MTPS and shed light on personalized probiotic supplements for consumers with different health status and the necessity that researchers and manufactures could explore novel probiotics as well as traditional ones.

Dietary Components That May Influence the Disturbed Gut Microbiota in Chronic Kidney Disease

Gut microbiota imbalance is common in patients with chronic kidney disease (CKD) and associates with factors such as increased circulating levels of gut-derived uremic toxins, inflammation, and oxidative stress, which are linked to cardiovascular disease and increased morbimortality. Different nutritional strategies have been proposed to modulate gut microbiota, and could potentially be used to reduce dysbiosis in CKD. Nutrients like proteins, fibers, probiotics, and synbiotics are important determinants of the composition of gut microbiota and specific bioactive compounds such as polyphenols present in nuts, berries. and fruits, and curcumin, may also play a key role in this regard. However, so far, there are few studies on dietary components influencing the gut microbiota in CKD, and it is therefore not possible to conclude which nutrients should be prioritized in the diet of patients with CKD. In this review, we discuss some nutrients, diet patterns and bioactive compounds that may be involved in the modulation of gut microbiota in CKD and provide the background and rationale for studies exploring whether nutritional interventions with these dietary components could be used to alleviate the gut dysbiosis in patients with CKD.

A possible link between polyunsaturated fatty acids and uremic toxins from the gut microbiota in hemodialysis patients: A hypothesis

INTRODUCTION

Indoxyl sulfate (IS) and p-cresyl sulfate (p-CS) are albumin-bound uremic toxins that are difficult to remove by hemodialysis (HD). Human serum albumin (HSA) carries several compounds, including fatty acids that can bind to site II of HSA and represent competing ligands for uremic toxins. The aim of this study was to investigate the association between fatty acids and uremic toxin plasma levels in patients undergoing HD.

METHODS

Thirty-three HD patients (51.5% male, 54.9 ± 10.2 years old, 44.63 ± 28.4 months on HD, albumin level of 3.8 ± 0.3 g/dL) were evaluated. The erythrocyte fatty acid content (saturated fatty acid [SFA], monounsaturated fatty acid [MUFA], and polyunsaturated fatty acid [PUFA]) was measured by gas chromatography, and total IS and p-CS plasma levels were measured by reversed-phase high-performance liquid chromatography.

FINDINGS

The mean percentages of docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) + DHA and gamma-linolenic (GLA) acid in the erythrocyte membrane were 1.35% ± 0.74%, 1.85% ± 0.79%, and 0.33% ± 0.26%, respectively. The mean levels of IS and p-CS were 19.4 ± 11.9 mg/dL and 101.5 ± 57.2 mg/dL, respectively. There was no significant association between SFA and MUFA and IS and p-CS; however, a negative correlation was found between p-CS and specific PUFAs, and the association between GLA and p-CS levels was retained after adjusting for potential confounding variables (β = -0.49, P = 0.007).

DISCUSSION

Polyunsaturated fatty acids may contribute to the decrease in p-CS uremic toxin plasma levels in patients with chronic kidney disease undergoing HD.

Impact of Gut Dysbiosis on Neurohormonal Pathways in Chronic Kidney Disease

Chronic kidney disease (CKD) is a worldwide major health problem. Traditional risk factors for CKD are hypertension, obesity, and diabetes mellitus. Recent studies have identified gut dysbiosis as a novel risk factor for the progression CKD and its complications. Dysbiosis can worsen systemic inflammation, which plays an important role in the progression of CKD and its complications such as cardiovascular diseases. In this review, we discuss the beneficial effects of the normal gut microbiota, and then elaborate on how alterations in the biochemical environment of the gastrointestinal tract in CKD can affect gut microbiota. External factors such as dietary restrictions, medications, and dialysis further promote dysbiosis. We discuss the impact of an altered gut microbiota on neuroendocrine pathways such as the hypothalamus⁻pituitary⁻adrenal axis, the production of neurotransmitters and neuroactive compounds, tryptophan metabolism, and the cholinergic anti-inflammatory pathway. Finally, therapeutic strategies including diet modification, intestinal alpha-glucosidase inhibitors, prebiotics, probiotics and synbiotics are reviewed.

Cranberries – potential benefits in patients with chronic kidney disease

Patients with chronic kidney disease (CKD) present many complications that potentially could be linked to increased cardiovascular mortality such as inflammation, oxidative stress, cellular senescence and gut dysbiosis.

Prebiotic, Probiotic, and Synbiotic Supplementation in Chronic Kidney Disease: A Systematic Review and Meta-analysis

OBJECTIVE

Gut dysbiosis has been implicated in the pathogenesis of chronic kidney disease (CKD). Restoring gut microbiota with prebiotic, probiotic, and synbiotic supplementation has emerged as a potential therapeutic intervention but has not been systematically evaluated in the CKD population.

DESIGN AND METHODS

This is a systematic review. A structured search of MEDLINE, CINAHL, EMBASE, Cochrane Central Register of Controlled Trials, and the International Clinical Trials Register Search Portal was conducted for articles published since inception until July 2017. Included studies were randomized controlled trials investigating the effects of prebiotic, probiotic, and/or synbiotic supplementation (>1 week) on uremic toxins, microbiota profile, and clinical and patient-centered outcomes in adults and children with CKD.

RESULTS

Sixteen studies investigating 645 adults met the inclusion criteria; 5 investigated prebiotics, 6 probiotics, and 5 synbiotics. The quality of the studies (Grades of Recommendation, Assessment, Development and Evaluation) ranged from moderate to very low. Prebiotic, probiotic, and synbiotic supplementation may have led to little or no difference in serum urea (9 studies, 345 participants: mean difference [MD] -0.30 mmol/L, 95% confidence interval [CI] -2.20 to 1.61, P = .76, I² = 53%), indoxyl sulfate (4 studies, 144 participants: MD -0.02 mg/dL, 95% CI -0.09 to 0.05, P = .61, I² = 0%), and p-cresyl sulfate (4 studies, 144 participants: MD -0.13 mg/dL, 95% CI -0.41 to 0.15, P = .35, I² = 0%). Prebiotic supplementation may have slightly reduced serum urea concentration (4 studies, 105 participants: MD -2.23 mmol/L, 95% CI -3.83 to -0.64, P = .006, I² = 11). Of the 2 studies investigating microbiota changes, synbiotic interventions significantly increased Bifidobacterium. Supplement effects on clinical outcomes were uncertain.

CONCLUSIONS

There is limited evidence to support the use of prebiotics, probiotics, and/or synbiotics in CKD management.

Tryptophan-Derived Uremic Toxins and Thrombosis in Chronic Kidney Disease

Patients with chronic kidney disease (CKD) display an elevated risk of thrombosis. Thrombosis occurs in cardiovascular events, such as venous thromboembolism, stroke, and acute coronary syndrome, and is a cause of hemodialysis vascular access dysfunction. CKD leads to the accumulation of uremic toxins, which exerts toxic effects on blood and the vessel wall. Some uremic toxins result from tryptophan metabolization in the gut through the indolic and the kynurenine pathways. An increasing number of studies are highlighting the link between such uremic toxins and thrombosis in CKD. In this review, we describe the thrombotic mechanisms induced by tryptophan-derived uremic toxins (TDUT). These mechanisms include an increase in plasma levels of procoagulant factors, induction of platelet hyperactivity, induction of endothelial dysfunction/ impairment of endothelial healing, decrease in nitric oxide (NO) bioavailability, and production of procoagulant microparticles. We focus on one important prothrombotic mechanism: The induction of tissue factor (TF), the initiator of the extrinsic pathway of the blood coagulation. This induction occurs via a new pathway, dependent on the transcription factor Aryl hydrocarbon receptor (AhR), the receptor of TDUT in cells. A better understanding of the prothrombotic mechanisms of uremic toxins could help to find novel therapeutic targets to prevent thrombosis in CKD.

Biotic Supplements for Renal Patients: A Systematic Review and Meta-Analysis

Intestinal dysbiosis is highly pervasive among chronic kidney disease (CKD) patients and may play a key role in disease progression and complications. We performed a systematic review and meta-analysis to evaluate effects of biotic supplements on a large series of outcomes in renal patients. Ovid-MEDLINE, PubMed and CENTRAL databases were searched for randomized controlled trials (RCTs) comparing any biotic (pre-, pro- or synbiotics) to standard therapy or placebo. Primary endpoints were change in renal function and cardiovascular events; secondary endpoints were change in proteinuria/albuminuria, inflammation, uremic toxins, quality of life and nutritional status. Seventeen eligible studies (701 participants) were reviewed. Biotics treatment did not modify estimated glomerular filtration rate (eGFR) (mean difference (MD) 0.34 mL/min/1.73 m²; 95% CI −0.19, 0.86), serum creatinine (MD −0.13 mg/dL; 95% confidence interval (CI) −0.32, 0.07), C-reactive protein (MD 0.75 mg/dL; 95% CI −1.54, 3.03) and urea (standardized MD (SMD) −0.02; 95% CI −0.25, 0.20) as compared to control. Outcome data on the other endpoints of interest were lacking, sparse or in an unsuitable format to be analyzed collectively. According to the currently available evidence, there is no conclusive rationale for recommending biotic supplements for improving outcomes in renal patients. Large-scale, well-designed and adequately powered studies focusing on hard rather than surrogate outcomes are still awaited.

The Role of Gut Microbiota and Diet on Uremic Retention Solutes Production in the Context of Chronic Kidney Disease

Uremic retention solutes (URS) are associated with cardiovascular complications and poor survival in chronic kidney disease. The better understanding of the origin of a certain number of these toxins enabled the development of new strategies to reduce their production. URS can be classified according to their origins (i.e., host, microbial, or exogenous). The discovery of the fundamental role that the intestinal microbiota plays in the production of many URS has reinstated nutrition at the heart of therapeutics to prevent the accumulation of URS and their deleterious effects. The intestinal microbiota is personalized and is strongly influenced by dietary habits, such as the quantity and the quality of dietary protein and fibers. Herein, this review out lines the role of intestinal microbiota on URS production and the recent discoveries on the effect of diet composition on the microbial balance in the host with a focus on the effect on URS production.